This project is a part of the Breast Cancer Cooperative Group's study of the hormonal therapy of advanced breast cancer. Implementation of the objectives of the Breast Cancer Cooperative Study Group is the purpose of this study. These objectives are outlined in the Breast Group protocol, originally approved by the Clinical Studies Panel, Cancer Chemotherapy National Service Center. Effective implementation of this method of group study is expected to result in progressive improvement in our understanding of steroid hormones and their clinical use as therapeutic agents in advanced cancer.